The present invention relates to a controller for controlling a controlled vehicle device. Hereinafter, the term “controlled vehicle device” refers to a device which is mounted on a vehicle and operated under the control of a controller. (The controller and the controlled vehicle device are sometimes also called a “vehicle device controller” and a “vehicle device”, respectively.) The present invention further relates to a method for detecting an anomaly in a temperature sensor mounted on a circuit board of the vehicle device controller.
Various controlled vehicle devices are known including, for example, a NOx sensor for detecting the concentration of NOx in exhaust gas, an oxygen sensor for detecting the concentration of oxygen in exhaust gas and a glow plug for heating a combustion chamber in a diesel engine, as disclosed in Patent Documents 1-3. These vehicle devices are connected to and controlled by a vehicle device controller.
In general, the vehicle device controller includes a circuit board having mounted thereon electronic circuit elements to control operations of the vehicle device. The vehicle device controller often further includes a temperature sensor mounted on the circuit board to detect a temperature of the circuit board and, even if an error or variations occur in the operations of the vehicle device under the influence of the temperature of the circuit board on the electronic circuit elements, collects such an error or variations in the operations of the vehicle device by the detected temperature of the circuit board.
For instance, Patent Document 1 discloses a controller for a NOx sensor that includes a control circuit board and a thermistor (as a circuit board temperature sensor) mounted on the circuit board to detect a temperature of the circuit board and corrects a NOx concentration detection value of the NOx sensor by the detected temperature of the circuit board.
The temperature of the circuit board cannot, however, be detected accurately in the event of an output anomaly (failure) in the temperature sensor. In this case, the NOx sensor controller of Patent Publication 1 cannot correct the NOx concentration detection value of the NOx sensor properly and generates an output signal responsive to the improperly corrected NOx concentration detection value. In order to avoid such a problem, it is required to properly detect the output anomaly (failure) in the temperature sensor.
On the other hand, Patent Document 4 discloses a controller for an engine that includes an ECU, an ECU temperature sensor mounted on the inside of the ECU to detect the inside temperature of the ECU (as a circuit board temperature sensor) and an exhaust temperature sensor fixed to an exhaust pipe of the engine to detect the temperature of exhaust gas in the exhaust pipe and, when the difference between a detection value of the ECU temperature sensor and a detection value of the exhaust temperature sensor is greater than a threshold value, judges the occurrence of an output anomaly (failure) in the ECU temperature sensor. Namely, the engine controller of Patent Document 4 is configured to detect the output anomaly in the circuit board temperature sensor based on the detection value of the circuit board temperature sensor and the detection value of the other temperature sensor located separately from the circuit board temperature sensor.    Patent Document 1: JP 2009-133834A    Patent Document 2: JP 2008-008667A    Patent Document 3: JP 2005-240707A    Patent Document 4: JP 2007-211714A